It sounds like you are using both grade 4/5 and grade5/6 books. Ifyou are teaching fifth grade and your kids have had Investigationsbefore I would recommend the following:

Math. Thinking at Grade 5 (this is not the same type of intro. book asthe Math. Thinking books at grades 3 and 4)

Picturing Polygons (2-D geometry)

Building on Numbers You Know

Name That Portion

The above units are all essential (in my humble opinion)

What you do after those really depends on what the kids have alreadydone. Maybe your district should make a long range plan so that themajor topics get covered over a 3 year span. For example, if you doChanges over Time and Seeing Solids and Silhouettes in 4th you may notwant to do Patterns of Change and Containers and Cubes in 5th. Ihighly recommend Between Never and Always since that probability stuffdoesn't show up any place else. Measurement Benchmarks is also a goodone to include since there isn't much measurement in 4th and there'sno volumetric measurement in the measurement unit in 3rd.